In transmission lines, different methods for fault detection and fault location may be used in order to locate accurately faulted place. For instance the most accurate solution in transmissions lines are utilizes the traveling wave principle—synchronized in time domain measurements from both ends of line. The computer device in a form of a fault locator monitors the traveling waves that are induced during appearing of faults. The waves are propagated from faulted place, with the velocity close to the speed of light in overhead lines, in both directions in transmission line. In the end of the transmission line the waves are detected and its times of arrival at the measuring points are determined.
From patent application WO2011127967A1 there is known a method and apparatus for determining the time of arrival of fault wave at a measurement point of power transmission system. The method is useful for localization a faulted place in transmission lines which is a homogeneous line. For long transmission mixed lines like overhead line and submarine cable or underground cable it is desirable to determine where such a fault occurs directly after the fault. The distance to the faulted place is proportional to the difference between times of arrival the first fault waves at measurement points in two stations and to the speed of the fault wave in transmission line. The distance to the fault can be determined with the accuracy of the synchronization device used for detection time of fault waves arriving. Usually the synchronization error is close to 200 ns. This invention is in general a double-ended method.
A single-ended transmission line fault locator is known from patent U.S. Pat. No. 4,766,549. A system for locating faults in a transmission line is presented. The system for locating faults in a high voltage direct current (HVDC) transmission lines uses measurements taken from only one end of the transmission line. The system comprises means for detecting transients, i.e. traveling waves, generated by a fault located in the transmission line and means for sorting by polarity detected transients for transients produced by a fault and transients reflected from the one end of the transmission line. Further the system comprises means for determination the arrival times of transients at one end of the transmission line and means for calculation the difference between the arrival times of such transients in order to determine the location of the fault. Such system is operating in a homogeneous type of transmission line—pure overhead line or pure cable line, but suffer some malfunctions when the transmission line is consisted from two or more different segments, overhead and cable segments, where each segment has different surge impedances and different wave propagation velocities, what causes additional wave reflections at junction point of such two segments. The present invention offers an improvement over the above discussed single-ended techniques.
The present invention is utilized a creation of a traveling waves schemes what is known for example from a literature “Transmission Lines and Wave Propagation”, by Philip C. Magnusson, Gerald C. Alexander, Vijai K. Tripathi, Andreas Weisshaar; 4th Edition, 2001, CRC Press LLC [chapter 3] for calculation the traveling wave pulses in a theoretical faulted point and theoretical arrival times of such pulses to the measuring points with a use a Bewley lattice diagrams.